Brill-Zinsser disease is a recrudescent form of infection with which agent?

• A. Rickettsia akari
• B. Rickettsia prowazekii
• C. Rickettsia typhi
• D. Rickettsia rickettsii

Answer: (B)

Brill-Zinsser disease is a recrudescent form of epidemic typhus caused by reactivation of latent infection with Rickettsia prowazekii. After an initial bout of epidemic typhus, the bacteria can persist in the body and reactivate years later, producing a milder illness that still resembles the original typhus—with fever, malaise, and a rash. Transmission is still typically via the human body louse, just like the primary disease. The other organisms listed cause different diseases: Rickettsia akari leads to rickettsialpox, Rickettsia typhi to murine typhus, and Rickettsia rickettsii to Rocky Mountain spotted fever. The defining idea here is that Brill-Zinsser disease is not a new infection with a different organism but a resurgence of disease from the same agent, Rickettsia prowazekii.